In the event that a voltage applied from a substation becomes excessive, an electric vehicle controller stops the operation of an inverter, opens a line breaker usually provided on a power supply path to an electric vehicle, and electrically separates the substation and the inverter in order to protect a switching device used in the inverter and a brake chopper circuit against the overvoltage. At this time, an overvoltage suppression thyristor is ignited to discharge an electrical charge in a filter capacitor via an overvoltage suppression resistor connected in series with the overvoltage suppression thyristor. As a result of these controls, the electrical charge in the filter capacitor is consumed in the overvoltage suppression resistor, thus the voltage of the filter capacitor drops.
Patent Literature 1 is an example of a conventional technology pertaining to the electric vehicle controller having the overvoltage suppression function. According to Patent Literature 1, current flowing through the overvoltage suppression resistor is commensurate with regenerative power at the time of regenerative braking, which can thus be continued without voltage being excessive.
Note that while Patent Literature 1 only discloses the overvoltage suppression function, it is common for an ordinary electric vehicle to have a configuration including a brake chopper circuit consuming the regenerative power together with an overvoltage suppression circuit as disclosed in Patent Literature 2, for example.